Proper dropdown active area and arrow placement (#7561)

Fixes #7423

Refactored widget matching algorithm to allow creating wrapper widgets even in cases where the widget config override is present. That allowed the widgets to be reordered, such that the argument name ends up being inside the dropdown widget. That way clicking it opens the dropdown.

Added explicit manual layout for the dropdown arrow position. Now it is positioned on the center of a selected appropriate child widget. For prefix chains, the leftmost part of the prefix application (the method or constructor) is selected.

https://github.com/enso-org/enso/assets/919491/86678b9d-c04e-4545-8d11-2d1e85b9b951

app/gui/language/span-tree/src/generate.rs

@@ -254,11 +254,12 @@ impl<'a> ApplicationBase<'a> {
         ApplicationBase { function_name, ..self }
     }
 
-    fn raw_node_data(&self) -> crate::node::ApplicationData {
+    fn raw_node_data(&self, is_prefix: bool) -> crate::node::ApplicationData {
         crate::node::ApplicationData {
-            suggestion_id:  None,
-            icon_name:      None,
+            suggestion_id: None,
+            icon_name: None,
             self_in_access: self.uses_method_notation,
+            is_prefix,
         }
     }
 }
@@ -312,11 +313,12 @@ impl ResolvedApplication {
         self.chain_arguments.push_front(argument)
     }
 
-    fn node_data(&self) -> crate::node::ApplicationData {
+    fn node_data(&self, is_prefix: bool) -> crate::node::ApplicationData {
         crate::node::ApplicationData {
-            suggestion_id:  self.suggestion_id,
-            icon_name:      self.icon_name.clone(),
+            suggestion_id: self.suggestion_id,
+            icon_name: self.icon_name.clone(),
             self_in_access: self.argument_in_access.is_some(),
+            is_prefix,
         }
     }
 }
@@ -381,8 +383,9 @@ impl SpanTreeGenerator for GeneralizedInfix {
         let kind = kind.into();
         let mut app_base = ApplicationBase::from_infix(self);
         let mut application = app_base.resolve(context);
-        let node_application =
-            application.as_ref().map_or_else(|| app_base.raw_node_data(), |r| r.node_data());
+        let node_application = application
+            .as_ref()
+            .map_or_else(|| app_base.raw_node_data(false), |r| r.node_data(false));
         if app_base.uses_method_notation {
             // This is a standalone method access chain, missing method parameters needs to be
             // handled here. It is guaranteed that no existing prefix arguments are present, as
@@ -558,7 +561,7 @@ fn generate_node_for_prefix_chain(
     let fallback_call_id = app_base.call_id;
     let mut application = app_base.resolve(context);
     let node_application =
-        application.as_ref().map_or_else(|| app_base.raw_node_data(), |r| r.node_data());
+        application.as_ref().map_or_else(|| app_base.raw_node_data(true), |r| r.node_data(true));
 
     // When using method notation, expand the infix access chain manually to maintain correct method
     // application info and avoid generating expected arguments twice. We cannot use the
@@ -800,7 +803,7 @@ fn generate_expected_argument(
     let arg_node = gen.generate_empty_node(InsertionPointType::ExpectedArgument { index, named });
     arg_node.node.set_argument_info(argument_info);
     arg_node.node.set_port_id(port_id);
-    gen.into_node(node::Kind::chained_infix(), None).with_extended_ast_id(extended_ast_id)
+    gen.into_node(node::Kind::ChainedPrefix, None).with_extended_ast_id(extended_ast_id)
 }
 
 /// Build a prefix application-like span tree structure where no prefix argument has been provided
@@ -1340,7 +1343,7 @@ mod test {
             sth_else => panic!("There should be 4 leaves, found: {}", sth_else.len()),
         }
         let expected = TreeBuilder::new(8)
-            .add_child(0, 8, node::Kind::chained_infix(), Crumbs::default())
+            .add_child(0, 8, node::Kind::ChainedPrefix, Crumbs::default())
             .add_child(0, 8, node::Kind::ChainedPrefix, Crumbs::default())
             .add_leaf(0, 3, node::Kind::Operation, PrefixCrumb::Func)
             .add_leaf(4, 4, node::Kind::prefix_argument().removable().indexed(0), PrefixCrumb::Arg)
@@ -1372,7 +1375,7 @@ mod test {
             sth_else => panic!("There should be 5 leaves, found: {}", sth_else.len()),
         }
         let expected = TreeBuilder::new(8)
-            .add_child(0, 8, node::Kind::chained_infix(), Crumbs::default())
+            .add_child(0, 8, node::Kind::ChainedPrefix, Crumbs::default())
             .add_child(0, 8, node::Kind::Operation, Crumbs::default())
             .add_leaf(0, 4, node::Kind::argument(), InfixCrumb::LeftOperand)
             .add_leaf(4, 1, node::Kind::Operation, InfixCrumb::Operator)

app/gui/language/span-tree/src/node.rs

@@ -56,6 +56,7 @@ pub struct ApplicationData {
     pub suggestion_id:  Option<usize>,
     pub icon_name:      Option<ImString>,
     pub self_in_access: bool,
+    pub is_prefix:      bool,
 }